﻿<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>文本框简单的单击效果</title>
    <script type="text/javascript" language="JavaScript">


    </script>
</head>
<body>

<input name="username" type="text"  onClick="this.value=''"  value="单击我试试" size="20" maxlength="20">

</body>
</html>